Building Extension Cost Calculator (2026 Prices)
Estimate the cost of your UK building extension based on size, specification, and extra requirements.
1. Building Extension Size
m²
2. Build Quality Rate (2026 Prices)
3. Premium Upgrades & Extras
Create Instant PDF Site Location Plans
Official Ordnance Survey mastermaps for planning applications.
From just £7.95
Create Planning MapEstimated Cost
Base Build Cost£52,000
Total (Excl. VAT)£52,000
Total (Incl. 20% VAT)£62,400
Disclaimer: This calculator provides general estimates based on representative 2026 UK build costs. Actual costs will vary significantly depending on location, ground conditions, structural requirements, and final specification. Always obtain itemised quotes from contractors.